1. Field of the Invention
The present invention relates to a paper feeder and an image forming apparatus.
2. Discussion of the Background
As conventionally known, image forming apparatuses include a paper feeder. The paper feeder loads recording media for image formation and stores the recording media. The paper feeder is capable of being put into and taken out from the body of the image forming apparatus in order to replenish and store recording media. The paper feeder includes a recording-media container and a width regulating member. The recording-media container houses recording media. The width regulating member regulates the width position of the recording media stored in the recording-media container (the width position is a position in a direction orthogonal to the conveyance direction of the recording media).
In feeding a recording medium, the width regulating member keeps the recording medium at a proper posture in the recording-media container while conforming to a predetermined conveyance standard position. For example, when the conveyance standard position is center standard position, the width regulating member often used is a pair of side regulating plates aligned in the widthwise direction of the recording media. The pair of side regulating plates are coupled to each other through a rack pinion mechanism and cooperate to move toward and away from each other in the widthwise direction of the recording media. In the rack pinion mechanism, the pinion gear is disposed on the inner bottom surface of the recording-media container. The rack is disposed at each of side regulating plates and meshes with the pinion gear at both sides of the pinion gear.
Japanese Unexamined Patent Application Publication No. 2000-7162 discloses a paper feeder that includes this type of side regulating plates. Specifically, a locking mechanism includes a locking pin and a pair of pinching racks. The locking pin is operable to move up and down on one of side regulating plates. The pair of pinching racks are fixed in the recording-media container and have a longitudinal dimension in the widthwise direction of the recording-media container. In order to fix the positions of the width regulating members with respect to recording media of an undefined size, the positions of the width regulating members are steplessly variable in the widthwise direction. Specifically, the pair of pinching racks are arranged to make their rack teeth face each other. Then, the locking pin is moved downward to force its engaging teeth at its lower end into the gap between the facing rack teeth. Thus, the engaging teeth are meshed with the facing rack teeth.
In the locking mechanism disclosed in Japanese Unexamined Patent Application Publication No. 2000-7162, the engaging teeth at the lower end of the locking pin are forced into the gap between the facing rack teeth. This ensures a firm mesh of the engagement tooth with both rack teeth. However, the firm mesh (position maintaining function) necessitates a high level of operation force for the up-and-down operation of the locking pin (locking operation and unlocking operation), leaving room for improvement in operability. In addition, the side regulating plates cooperate to move toward and away from each other in the widthwise direction, whereas the locking pin is operated upward and downward orthogonal to the widthwise direction. Thus, in the series of actions, it has been impossible to implement a one-touch action to move the locking pin upward and downward while moving the side regulating plates in the widthwise direction. Instead, it has been necessary to perform the up-and-down operation and the moving operation in the widthwise direction individually, leaving room for improvement in operability.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a locking mechanism of a width regulating member having both the good operability and the good position fixing function.